Multiple lines of experimental evidence point to the involvement of endogenous opiates in appetite regulation. Post brain injury patients often exhibit driven eating behaviour. Since this problem fails to respond to behaviour modification, appetite suppressants, lithium, or any other usual approach, the use of the oral narcotic antagonist, Naltrexone, was given to three such patients. Naltrexone binds multiple opiate receptor sites in the hypothalamus, including the kappa receptors which have been implicated in appetite regulation, the use of this narcotic antagonist in hypothalamic hyperphagia appears to be a rational approach to this intractable problem.In this open trial, lasting from 4 1/2 to 9 months, the minimal effective dose appeared to be in the range of 100 mg per day. No side-effects (for example elevations in liver enzymes) were noted.All of the patients had an improved sense of well-being and their behaviours were less difficult to manage when on the Naltrexone.The significance of this preliminary trial is that narcotic antagonists may have a role in the treatment of brain-injured patients with bulimia. Also, Naltrexone may be useful in treating other maladaptive behavioural consequences of head trauma such as stealing, manipulation, demandingness, and depression. Likewise, the effects on the deranged endocrine system, such as the hypogonadism, are significant and deserve further exploration.